Electromagnetically coupled hearing aid



F. W. LEWIS ELECTROMAGNETICALLY COUPLED HEARING AID March 17, 1964 2 Sheets-Sheet 1 Filed Feb. 8, 1960 n Q Q Q 3 N I. .1 II E- t -.-i I. a EE \W INVENTOR. F. Win48 in: za uw Arman/m March 17, 1964 F. w. LEWIS ELEGTROMAGNETICALLY COUPLED HEARING AID 1 run/any 2 Sheets-Sheet2 Filed Feb. 8, 1960 v mu. 5 in M 4 F L f ln.\, a can A? a 7 8 Z 1 Q 5 lrronmsrs United States Patent O 3,125,646 ELECTROMAGNETHCALLY CDUPLED HEARING AID Frederick Willard Lewis, Brooklyn Center, Minn, assignor, by rnesne assignments, to The Telex Corporation, Tulsa, kla., a corporation of Delaware Filed Feb. 8, 1960, Ser. No. 73% 8 Qlairns. (Cl. 179-107) This invention relates to hearing aids and hearing aid construction, and more particularly to hearing aids having no physical connection between the hearing aid microphone and the output sound transducer.

Several types of hearing aids have been designed to conceal or hide the telltale electrical leads or audio tube which in air conduction type hearing aids extend into the users ear. Further the microphone and output transducer in a hearing aid are often mechanically connected providing a feedback path which can cause sound distortion. The present invention completely eliminates both of the above described objectionable features by electromagnetically coupling an amplified signal from a sound input unit on a users body or head to a sound output unit attached to the users head. The output unit intercepts the input units electromagnetic waves and converts same into sound vibrations. The output unit may be inside an ear mold insertable into the users outer ear passageway, substantially out of view, to provide amplified sound vibrations to the users ear drum.

In a modification of the invention a bone conduction unit is separately attached to the users head; the same input unit being usable with either type of output unit. Further it has been found that simultaneous use of bone conduction and air conduction type output units can greatly improve the users benefit from an aid.

The input unit may be enclosed in an eyeglass templar member or may be worn elsewhere on the users body. In any event there is preferably no physical connection between the input and output units.

Accordingly it is an object of this invention to provide a hearing aid having physically independent and electromagnetically coupled sound input and sound output units.

It is another object to provide a sound output unit insertable into a users ear passageway substantially out of view.

It is a further object to provide a hearing aid sound input unit attachable to a users body and with an electromagnetic wave generating coil which directs the waves toward the users ear.

It is a still further object to provide an electromagnetically coupled hearing aid having a modulated carrier frequency for transferring amplified electrical signals to a sound output unit.

It is another object to provide a hearing aid which produces both air and bone conducted amplified sound waves.

These and other more detailed and specific objects will be disclosed in the course of the following specification, reference being had to the accompanying drawings, in which- FIG. 1 is a side elevational view of the presently preferred embodiment of the air conduction type hearing aid as attached to a users head in operating position.

FIG. 2 is a cutaway side elevational view in approximately actual size of a sound input unit installed in an eyeglass templar member as seen in FIG. 1.

FIG. 3 is a side elevational View of a combined air and bone conduction type of hearing aid showing a modified attachment for a sound input unit.

FIG. 4 is a schematic diagram of the sound input and output units electrical circuits with their respective inductances axially aligned for maximum power transfer.

FIG. 5 is an actual size elevational view of an air conduction type sound output unit as first used with this invention.

FIG. 5A is an enlarged end elevational view of an air conduction type sound output unit with a cutaway portion showing the axial alignment of a lumped inductance installed inside an ear mold, insertable into a users ear canal.

FIG. 6 is an end elevational view of the FIG. 5 unit.

FIG. 6A is a vertical sectional view taken in the direction of the arrows along the line 6A6A in FIG. 5A.

FIG. 7 is a schematic diagram of a passive sound output unit.

FIG. 8 is an audiograph showing the audio frequency responses of the FIG. 1 embodiment and a prior art single unit air conduction type hearing aid.

With more particular reference now to the accompanying drawing like numbers denote like parts and structural features in the various figures. In FIG. 1 there is shown a sound input unit 10 mounted inside an eyeglass templar member 12 and a sound output unit 14 inserted into a users ear passageway. The input unit 10 consists of a microphone or input transducer 16 connected to the input of a transistorized audio signal class A amplifier 18. The amplifier 18 is connected to modulator-oscillator 20 having a carrier frequency determination circuit including the slug tuned coil 22. The coil 22 is mounted in the downwardly extending rear portion 24 of the templar member 12 and with the coil axis, indicated by the line 2d, intersecting the output unit 14. As the microphone i6 detects sound vibrations, the amplifier 18 modulates the modulator-oscillator 2i frequency to provide a sound modulated electromagnetic wave having its greatest intensity along axis 26. The unit 14 has a coil 28 (FIG. 5) which intercepts the wave. The unit 14 converts same into amplified sound vibrations directed at the users ear drum, as will become apparent.

A modification of the FIG. 1 embodiment is shown in FIG. 3 wherein the sound input unit 10 is mounted in a body supported case 30, as by the shoulder straps IiilA. The coil 22 now includes the wires 32 which circumscribe the users neck hidden from view under a shirt collar or dickey (not shown), as the case may be. A sound output unit 14, the same as the FIG. 1 unit 14, is inserted into the users ear passageway. Operation of the two embodiments is identical save that the power requirements of the FIG. 3 modification are greatly increased because of the increased spacing between the coils 2.8 and 22 as embodied in the wires 32.

Improved operation is provided by adding a bone conduction type sound output unit 34 supported against the users head by a head clip 34A. The sole difference between the two units 14 and 34 is in the output transducer. It is understood that the unit 34-34A may be used with the FIG. 1 preferred embodiment with equal facility for providing both air and bone conduction of amplified sound waves.

The electronic circuits of the sound input unit 10 will now be described with particular reference to FIG. 4. The microphone 16 in response to sound waves 16A induces a signal in the coil 36 to vary in a usual manner the transistor 38 base drive current. The transistor base DC. bias is provided through the resistance 48 and switch 41 from the subminiature battery cell 42. The capacitor 44 serves to couple the signal (A.C. coupling) from the coil 36 to the transistor 38. The resultant audio frequency electrical signal is amplified by the capacitively coupled amplifier 18 including the class A operated transistors 38, 46 and 48. A volume control is provided at St The amplified signal is transferred to the base electrode of the emitter follower transistor 52 in the modulator-oscillator 20. The emitter follower 52 controls the collector current amplitude of the carrier frequency oscillator transistor 54 to amplitude modulate the oscillator frequency. The Hartley oscillator includes the coil 22 in its inductive-capacitive frequency determination portion 55. The coil 22 current magnitude varies with the transistor 54 collector current changes as is well understood by those skilled in the art.

The modulator-oscillator 20 is tuned by the axially adjustable magnetically permeable slug 56 in the coil 22. The carrier frequency is preferably between 150 kc. and 250 kc. for permitting small size components while avoiding the difiiculties often encountered with much higher frequencies. Alternately the audio frequency electrical signal may be directly provided to the coil 22 as by connecting the coil 22 between the transistor 52 emitter and the plus terminal of battery 42.

The coil 22 serves as a helical transmitting coil with the modulated carrier electromagnetic wave being strongest along the aligned axes 26 and 58. The slug 56 permits tuning for maximum power transfer easier. The carrier frequency usage also increases the insensitivity of unit 14 to interference from electrical power lines.

The output sound unit 14 coil or lumped inductance 28 is preferably axially aligned with the coil 22 for maximum coupling therebetween. With momentary reference to FIG. 1 the unit 14 coil is so aligned by mounting the unit 14 into a preformed plastic ear mold, such as seen in FIG. and inserting the mold into the outer ear aligns the coils 22 and 28. With the FIG. 5A mold, it is tuned for maximum sound level and inserted into the ear canal.

When initially using the input sound unit 18 with a different unit 14 or 34, it is desirable that the modulator 20 oscillator be retuned for matching the modulator carrier frequency with the output unit tuned circuit frequency.

In the modification of this invention using both air and bone conduction, it is preferred that both the units and 34 respective coils be tunable to match the frequency of the unit 14 circuits.

It should be noted that the coil or inductance 22 of FIG. 1 is vertically elongated. This serves to provide a maximum electromagnetic wave intensity traversing a vertically widened horizontally extending plane along the side of the users head. This provision introduces a tolerance whereby there is good coupling between the units for users with differently shaped earsmaking the aid usable to best advantage by a greater number of people. Further the vertical positioning of the output unit 34 on a users head with the FIG. 1 unit 10 is less critical with the elongated coil than with a round coil.

The sound output units 14 and 34 may have identical electronic circuits. In the preferred output unit circuit the tuned tank circuit consisting of the coil 28 and shunt capacitor 60 has a portion of the coil connected between the base and emitter electrodes of a transistor 62. The audio frequency modulated carrier electromagnetic wave is intercepted by the coil 28 to vary the transistor 62 conductivity of the modulating audio frequency rate. A subminiature cell 64 provides current through the tranusers ear canal with the aperture 70 on the inner end.

In both molds the speaker 66 is inside a box having the sound aperture 72 next to the passageway 70. As seen in FIG. 1 the mold 68 places the coils 22 and 28 closely adjacent each other on respective sides of the outer ear and this mold is preferred for that reason.

The coil 28 is mounted separately from the other components to reduce the effects of detuning the tank circuit 2860. The transistor 62 and the capacitors are mounted in a box 74 disposed in a non-interfering manner with respect to coil 28 as seen in FIG. 5. Note the coil 28 axis 58 does not intersect either the transducer 66 or box 74.

A completely passive sound output unit 34 is illustrated in FIG. 7 wherein the tank circuit 28A-60A is coupled by the semi-conductor diode detector 76 to the inductance or coil 78. The output transducer, diagrammatically indicated by the symbol 80, is mechanically vibrated by the coil 78 in a usual manner to reproduce sound waves through the users bones as at 82. It is understood that the speaker 66 may be substituted for the output transducer 78-80, and vice versa, in the two illustrated sound output units.

The output transducer 7880 may be of the usual bone conduction type wherein the coil 78 is held in a first mass 78A. The current magnitude variations in the coil 78 cause the magnetic mass 78 to vibrate providing the bone conducting waves 82A. Mass 78A must be greater than mass for causing it to vibrate.

The audio frequency response of the FIG. 1 embodiment is shown as line 84 in the FIG. 8 audiograph. The line 86 is an audiograph of a single unit hearing aid, i.e., one in which there is a physical connection between the microphone and the output transducer. The several peaks 88 result from mechanical vibrational feedback. Note the audiograph 84 provides a somewhat smoother and broader frequency response curve indicating a higher fidelity sound reproduction.

It is understood that suitable modifications may be made in the structure as disclosed, provided such modifications come within the spirit and scope of the appended claims. Having now therefore fully illustrated and described my invention, what I claim to be new and desire to protect by Letters Patent is:

l. A hearing aid having two physically separate and independent units comprising in combination: an eyeglass templar member having a downwardly extending rear portion adapted to fit over and behind a users ear and being adapted to be carried by an eyeglass frame; a first unit mounted within said templar member and including a microphone, a signal amplifier, and a carrier frequency modulator-oscillator means having a frequency determining circuit including an inductance disposed in the downwardly extending rear portion of said templar member and circuit means interconnecting all of said last named devices in electrical cooperating relationship whereby a modulated carrier frequency output signal is emitted from the inductance for coupling the electromagnetic output thereof to a second unit; and a second unit mounted within a preformed ear mold having a second outlet and adapted to be positioned within a users auditory canal, said second unit including a sound output transducer, a capacitor-inductor tank circuit tuned to the carrier frequency output of said first unit, and means, including demodulating means, interconnecting said tank circuit and said transducer, said inductor being positioned in electromagnetic signal receiving relationship to the inductance in said first unit.

2. A hearing aid of the class above described wherein two separate units are adapted to be electromagnetically coupled to transmit amplified sound energy impingent thereon to the auditory canal of a user, comprising in combination: a first unit contained within an eyeglass templar member adapted to be mounted upon an eyeglass frame and which has a downwardly curved rear portion to be positioned over and behind a users outer ear in a substantially vertical plane and having a sound transmitting aperture therein, transducing means, electrical signal generating means and a coil mounted within said member so that the coil is disposed in the rear portion of said member and the axis thereof is in said vertical plane, and circuit means interconnecting said transducing means, signal generating means and coil whereby the coil may be energized to transmit a signal comprised of electromagnetic energy along said axis; and a second unit including an ear mold having an aperture therein, an output transducer and a coil mounted within said mold, said output transducer being in sound energy transmitting relationship to the aperture, said coil being mounted whereby its axis is substantially coincident with the axis of the coil in said first unit, and electromagnetic energy responsive circuit means interconnecting said transducer and said last named coil.

3. In a hearing aid comprising two electromagnetically coupled units, the combination comprising; a first unit being mounted within an eyeglass frame templar member which has a downwardly extending rear portion adapted to fit over and behind a users ear, and a sound transmitting aperture therein, microphone means, modulating means, and a vertically elongated inductance means positioned in said downwardly extending rear portion, circuit means interconnecting said microphone means, said modulating means and said inductance means so as to provide a field of electromagnetic energy primarily along a predetermined axis of said inductance means in response to signals applied thereto; and an ear mold for positioning entirely within a users ear, said mold having an aperture in one end, transducer means in sound transmitting relation to said aperture and electromagnetic field detecting means drivingly connected to said transducer means, said field detecting means including a coil having an axis to be positioned in substantial parallelism to said predetermined axis when both of said units are in engagement with a users ear, said transducer means and said electromagnetic field detecting means being mounted within said ear mold.

4. In a hearing aid including a transmitter and two separate and independent receiving units, the combination comprising; a transmitting unit including a microphone, a modulator connected to said microphone and a lumped inductance, connected to said modulator for radiating electromagnetic waves; a first receiving unit being adapted for being inserted into the auditory canal of a user and including a lumped inductance for intercepting said electromagnetic waves and signal demodulating sound output transducer means electrically connected to named lumped inductance for converting said intercepted electromagnetic waves into amplified sound waves; and a second receiving unit having a like lumped inductance and a signal demodulating bone conduction type sound output transducer connected thereto, and attaching means on the second receiving unit for holding it on a users head such that the lumped inductance intercepts said radiated electromagnetic waves whereby the output of the transmitting unit is simultaneously applied to each of said first and second receiving units.

5. A hearing aid comprising two separate electromagnetically coupled units, one unit being inside an eyeglass frame templar member having an aperture and which has a downwardly curved rear portion to be positioned over and behind a users outer ear in a substantially vertical plane, sound detecting, electrical signal generating means and a coil mounted within said member said coil being positioned in the rear portion of said member and having an axis in said plane directed toward the ear of a user the said last and being elongated along the vertical plane, and circuit means interconnecting said sound detecting means, said signal generating means and said coil whereby said coil is energized in accordance with sound impingent on said sound detecting means to radiate an electromagnetic signal substantially along said axis; the other unit comprising an ear mold having an aperture, an output transducer and a second coil mounted inside said mold, said coil having an axis to be positioned substantially coincident with the axis of the coil in said one unit, and circuit means interconnecting said transducer and said coil.

6. A hearing aid comprising sound transducing means including a microphone, modulating means and inductive output means connected so as to provide an electromagnetic signal output and contained in a sound permeable single case mountable on a users body in a first predetermined position said coil having a preferred axis of radiation directed toward the ear of a user, a first sound output means including a coil, detector means and a speaker connected in signal translating relationship, for insertion substantially completely into a users ear so that said coil and said inductive output means are electromagnetically coupled and said speaker is in sound transferring relationship with the users ear drum, and a second sound output means including holding means for firmly attaching the same against a users head for transferring sound vibrations thereinto by bone conduction said second means including a coil, detecting means and bone conduction transducing means connected in signal translating relationship so that said last named coil and said inductive output means are electromagnetically coupled whereby said first and second sound output means are simultaneously energized and operable in response to the electromagnetic signal output of said inductive output means in Said sound transducing means.

7. An electromagnetically coupled hearing aid comprising a transmitter and two physically separated and independent receivers, said transmitter having interconnected microphone means, modulating means and electromagnetic field generating means, said generating means terminating in a long wire loop for positioning around a users neck, one receiver including interconnected helical coil means, detecting means and sound output transducer means mounted within a preformed ear mold insertable entirely into a users auditory canal so that the axis of said coil means is substantially vertical and the transducer means is in sound vibration communicative relation to the users ear drum, the other receiver having attaching means adapted to firmly press the receiver against a users head for transferring sound waves thereinto said receiver including a helical coil, detecting means and bone conduction transducing means connected in signal receiving cooperative relationship so that the axis of said coil is substantially vertical and the bone conduction transducing means is in sound vibration communicative relation to the users head whereby the output of said transmitter is simultaneously applied through electromagnetic coupling to each of said receivers.

8. A hearing aid comprising two separate electromagnetically coupled units, one unit being inside an eyeglass frame templar member having an aperture and which has a downwardly curved rear portion to be positioned over and behind a users outer ear in a substantially vertical plane, sound detecting means, modulator means and a coil mounted within said member said coil being positioned in the rear portion of said member and having an axis in said plane directed toward the ear of a user and being elongated along the vertical plane, and circuit means interconnecting said sound detecting means, said modulator means and said coil whereby said coil is energized in accordance with sound impingent on said sound detecting means to radiate an electromagnetic signal substantially along said axis; the other unit comprising an ear mold having an aperture, an output transducer and a second coil mounted inside said mold, said coil having an axis to be positioned substantially coincident with the and said coil.

References Cited in the file of this patent Potter Sept. 25, 1951 5 UNITED STATES PATENTS Kelly Aug. 7, 1934 Lybarger Dec, 4, 1934 Perlman May 18, 1943 10 Olson Feb. 8, 1949 5% Thomas Nov. 20, 1956 Williams Nov. 19, 1957 Hollingsworth Mar. 29, 1960 Hollingsworth Mar. 29, 1960 Mitchell et a1 Aug. 23, 1960 FOREIGN PATENTS Great Britain Sept. 26, 1956 Great Britain Dec. 23, 1957 Great Britain July 30, 1958 

1. A HEARING AID HAVING TWO PHYSICALLY SEPARATE AND INDEPENDENT UNITS COMPRISING IN COMBINATION: AN EYEGLASS TEMPLAR MEMBER HAVING A DOWNWARDLY EXTENDING REAR PORTION ADAPTED TO FIT OVER AND BEHIND A USER''S EAR AND BEING ADAPTED TO BE CARRIED BY AN EYEGLASS FRAME; A FIRST UNIT MOUNTED WITHIN SAID TEMPLAR MEMBER AND INCLUDING A MICROPHONE, A SIGNAL AMPLIFIER, AND A CARRIER FREQUENCY MODULATOR-OSCILLATOR MEANS HAVING A FREQUENCY DETERMINING CIRCUIT INCLUDING AN INDUCTANCE DISPOSED IN THE DOWNWARDLY EXTENDING REAR PORTION OF SAID TEMPLAR MEMBER AND CIRCUIT MEANS INTERCONNECTING ALL OF SAID LAST NAMED DEVICES IN ELECTRICAL COOPERATING RELATIONSHIP WHEREBY A MODULATED CARRIER FREQUENCY OUTPUT SIGNAL IS EMITTED FROM THE INDUCTANCE FOR COUPLING THE ELECTROMAGNETIC OUTPUT THEREOF TO A SECOND UNIT; AND A SECOND UNIT MOUNTED WITHIN A PREFORMED EAR MOLD HAVING A SECOND OUTLET AND ADAPTED TO BE POSITIONED WITHIN A USER''S AUDITORY CANAL, SAID SECOND UNIT INCLUDING A SOUND OUTPUT TRANSDUCER, A CAPACITOR-INDUCTOR TANK CIRCUIT TUNED TO THE CARRIER FREQUENCY OUTPUT OF SAID FIRST UNIT, AND MEANS, INCLUDING DEMODULATING MEANS, INTERCONNECTING SAID TANK CIRCUIT AND SAID TRANSDUCER, SAID INDUCTOR BEING POSITIONED IN ELECTROMAGNETIC SIGNAL RECEIVING RELATIONSHIP TO THE INDUCTANCE IN SAID FIRST UNIT. 